Yeah its a good idea... The alloy you are thinking of is 6061 T6, which is the highest grade automotive round. 7071 T6 is the flat plate you need.

I've designed some up already, and was going to make them soon.

Also make sure you use reasonably good rose joints, as they make all the difference.

If you want to check out my design let me know, and l'll capture some jpegs of the drawings.

If you can get them machined free, or really cheap then l'll be very interested!!